Expansion device



May 14, 1929. L. H. HILL EXPANSION DEVI CE Filed D80- 25. 192? INVENTQRLe/and Hf/i/l XLVITNESSES:

Patented May 14, 1929.

UNIT STATES 1,712,765 PATENT OFFICE.

LELAND H. HILL, OF WILKINSBURG, PENNSYLVANIA, ASSIGNOR TO WESTINGHOUSEELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

EXPANSION DEVICE.

Application filed December as, 1922. Serial No. 608,792.

My invention relates to expansion devices, and it has particularrelation to such 'devices as may be employed in connection withtransformers, circuit breakers and electrical apparatus of a similarnature.

One object of my invention is to provide a structure wherein a body ofgas is retained above the level of the insulating oil in the tank toconstitute a cushion for such shocks as may occur by a sudden evolutionof gas within the enclosing casing.

A second object of my invention is to provide an expansion device thatis so related to the main tank that the oil in the latter is maintainedout of contact with the atmosphere and substantially free from theeffects of oxidation.

A further object of my invention is to provide a structure wherein abody of gas above the insulating oil in the tank may be maintained atsubstantially constant pressure and constant volume during fluctuationsin temperature and volume of the insulating oil.

In the operation of transformers, circuit breakers and the like, it hasbeen found that the insulating oil for covering the apparatusdeteriorates very rapidly when it is in contact with the atmosphere.Considerable moisture is absorbed, thereby diminishing thev insulatingproperties of the oil. In addition, the explosive mixtures of air andhydrocarbon gases may form within the tank.

I provide a body of inert gas, such as nitrogen or other suitable gas,which fills the space above the insulating oil in the main tank. Anexpansion device that is connected to the main tank below the level ofthe insulating oil is of such capacity and is so disposed relatively tothe main tank that increases in the volume of the insulatingoil mayoccur without materially increasing the pressure applied to the inertgas and without materially diminishing the volume occupied by the gas.

In the accompanying drawing,

Figure 1 is a view, partially in elevation and partially in section, ofa tank for electrical apparatus with'my invention applied thereto; and

Fig. 2 is a similar view of a modified form I of my invention.

Referring to Fig.1, a tank 1, which maybe of any conventional form forenclosing a transformer, circuit breaker or other apparatus, illustrateddiagrammatically by the reference character 1, is partially filled withinsulating oil to a level indicated at 3. The space 4 above theinsulating oil is filled with inert gas which may be supplied in anysuitable manner. The cover 5 of the casing is attached to the tank inany suitable airtight manner.

An expansion device 6, that is connected to the tank 1 by means of. apipe 7 at a point considerably below the level of the oil 2, comprisesan auxiliary tank 8 that is normally filled with oil, indicated at 9, tothe same level as that of the tank 1. The upper portion of the tank 8 isprovided with a vent pipe 10. The lower portion of the casing isprovided with a drain pipe 11 that is controlled by a suitable valve 12.

When the temperature of the apparatus 1 and th at of the surroundinginsulating oil increases, the volume of the oil increases to acorresponding degree. The result is to tend to increase the pressureapplied to the-gas in the space 4 by reason of the increased volume ofthe oil. The oil, accordingly, flows through the pipe 7 into theauxiliary tank 8 to cause the oil in the latter to assume a level abovethe level 3, at such height as to correspond to the increased pressurein the main tank 1.

If the auxiliary tank 8 is of large capacity relatively to the volume ofoil to be transferred from the main tank, the pressure ap plied to thegas in the space 4 is relatively small.- The volume of the gas isaccordingly diminished to a correspondingly small degree.

When the temperature decreases, oil flows from the auxiliary tank 8through the pipe 7 into the main tank 1'. The level of the oil in theauxiliary tank falls in accordance with the changes in pressure. Duringthis operation, air enters through the vent pipe 10 to occupy the spaceabove the oil in the auxiliary tank.

lit will be obvious that, during the operation of breathing or exchangesof oil between the main and the auxiliary tanks, the quantity of inertgas in the space 4 remains the same and that its volume and pressure arenot materially afiected by changes in temperature of the nil. It will beunderstood also that, by reason of the location of the connection of thepipe 7 to the main tank, the external atmosphere is never in contactoxidation or slud'ging as may occur takes.

place in the auxiliary tank. The sludge and any moisture that may havesettled in the auxiliarytank may be removed by means of the drain pipe11 and valve 12.

Reference may now be had to the structure shown in Fig. 2. The apparatusshown therein is similar in principle and operation to that shown inFig. 1. The expansion device differs in structural details in that itcomprises an annular auxiliary tank 14 that surrounds the main tank 1 atits upper portion. The auxiliary tank is connected to the main tankbelow the level of the insulating oil by suitable openings 15. A ventpipe 16 and a drain pipe 17, with its controlling valve 18, performfunctions similar to those described in connection "with the apparatusof Fig. 1. In view of the detailed description of the'operation of theapparatus of Fig; 1, a detailed description of the operation of Fig. 2is omitted as unnecessary to an understanding of the operation of thisform of my invention.

In case of the sudden evolutioniof gases by containing a gaseous mediumabove the oil level at substantially atmospheric pressure.

4;. The combination with acasing containing insulating oil, of anelectrical translating device immersed in said oil, a cushion of inertgas confinedwithin said casing above the oil and in contact therewith,an expansion chamber partially filled with insulating oil, there beingcommunication independent of said gas cushion between the oil in saidcasing and the oil in said expansion chamber to permit interchange ofoil between the casing and exreason of a fault in the electricalapparatus or for any other reason, the body of gas in the space 4operates as a' cushion to absorb the initial impact of the shock causedthereby.

.This arrangement may diminish the shock sufiiciently to enable thestructure of the tank to. withstand the stresses to which it issubjected. This result is a very desirable one because serious damage tolife and property may occur if hot or burning oil is permitted to escapefrom the tank 1.

In addition to providing a cushion for shocks, the body of inert gasprevents the formation of explosive mixtures and the deterioration ofthe oil by oxidation. The above and other advantages will be apparent tothose skilled in the art to which my invention appertains.

I claim as my invention r 1. The combination with a tank for electricalapparatus, a quantity of oil for partially filling said tank, and aquantity of inert gas occupying the space above the oil, of means forpermitting the expansion of said oil without correspondingly increasingthe pressure applied to said gas, said means comprising an auxiliarytank for containing oil, a connection betwenthe two tanks, below the oillevel, said auxiliary tank having a vent opening to the outside air'above the oil level.

2. The combination with a tank for electrical apparatus, a quantity ofoil for partially filling said tank, and a quantity of inert gasoccupying the space above the oil, of means for permitting the expansionof said 'oil without affecting the pressure applied to said gas and itsvolume in said tank, to corresponding degrees, said means comprising anauxiliary tank for containing oil, a connection between the two tanksbelow the oil level, said pansion chamber due to thermal expansion andcontraction of the oil in the casing, and

means for maintaining said expansion chamber substantlally atatmospheric pressure in the region thereof above the level ofthemsulating oil therein. I

5. The combination with a casing, of a transformer in said casing, anexpansion chamber spaced from said casing, a conduit communicating withsaid expansion chamber and with said casing in a region removed from thetop thereof, the cross-sectional area of said conduit being smallcompared e u with the cross-sectional area of said expansion chamber,aninsulating liquid medium disposed in said expansion chamber, theconduit leading therefrom and in said casing to a level abovesaidregion, of an inert gas cushion confined within said casing andcontacting with the upper surface of said liquid medium, and aconnection leading from said expansion chamber and open to theatmosphere.

6. Thecombination with a casing, of a transformer in said casing, anexpansion chamber, a conduit'communicatin with said expansion chamber,and with sai casing in a region removed from the top thereof, aninsulating liquid medium disposed in said expansion chamber, the conduitleading therefrom and in said casing to a level above said region, agaseous cushion confined within said casing and contacting with theupper surface of said liquid medium, and a connection leading from saidexpansion chamber-and open to the atmosphere. I

In testimony whereof, I have herento sub- :SlCIlbed my name this 21stday of December,

LELAND HILL.

